1. Technical Field
The present disclosure generally relates to electrosurgery. More particularly, the present disclosure relates to systems and methods for calibrating power measurements within an electrosurgical generator.
2. Background of Related Art
Electrosurgery involves the application of high-frequency electric current to cut or modify biological tissue during a surgical procedure. Electrosurgery is performed using an electrosurgical generator, an active electrode, and a return electrode. The electrosurgical generator (also referred to as a power supply or waveform generator) generates an alternating current (AC), which is applied to a patient's tissue through the active electrode and is returned to the electrosurgical generator through the return electrode. The alternating current typically has a frequency above 100 kilohertz to avoid muscle and/or nerve stimulation.
During electrosurgery, the alternating current generated by the electrosurgical generator is conducted through tissue disposed between the active and return electrodes. The tissue's impedance converts the electrical energy (also referred to as electrosurgical energy) associated with the alternating current into heat, which causes the tissue temperature to rise. The electrosurgical generator controls the heating of the tissue, by controlling the electric power (i.e., electrical energy per time) provided to the tissue. Although many other variables affect the total heating of the tissue, increased current density usually leads to increased heating. The electrosurgical energy is typically used for cutting, dissecting, ablating, coagulating, and/or sealing tissue.
The two basic types of electrosurgery employed are monopolar and bipolar electrosurgery. Both of these types of electrosurgery use an active electrode and a return electrode. In bipolar electrosurgery, the surgical instrument includes an active electrode and a return electrode on the same instrument or in very close proximity to one another, usually causing current to flow through a small amount of tissue. In monopolar electrosurgery, the return electrode is located elsewhere on the patient's body and is typically not a part of the electrosurgical instrument itself. In monopolar electrosurgery, the return electrode is part of a device usually referred to as a return pad.
An electrosurgical generator includes a controller that controls the power applied to a load, i.e., the tissue, over some period of time. The power applied to the load is controlled based upon the power determined at the output of the electrosurgical generator and a power level set by the user or a power level needed to achieve a desired tissue effect. The power at the output of the electrosurgical generator is determined by measuring the voltage and current at the output of the electrosurgical generator and calculating the average power based upon the measured voltage and current.
The voltage and current measured by the sensors at the output of the electrosurgical generator, however, may not equal the actual voltage and current applied to the load, i.e., the tissue, because of errors in the voltage and current measurements. These measurement errors may be caused by parasitics in the cable connecting the electrosurgical generator to the electrosurgical instrument, parasitics in the analog processing circuitry, and/or delays of the analog to digital conversion process. As a result, the power calculations may be inaccurate and may lead to improper control of the electrosurgical energy applied to the tissue.